linux-kernel - [PATCH 4.19 14/44] block/bio: Do not zero user pages

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Message-Id: <20181218163929.193192006@linuxfoundation.org>
Date:   Tue, 18 Dec 2018 17:39:26 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Todd Aiken <taiken@...ech.ca>,
        Laurence Oberman <loberman@...hat.com>,
        Bart Van Assche <bvanassche@....org>,
        Keith Busch <keith.busch@...el.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 4.19 14/44] block/bio: Do not zero user pages

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Keith Busch <keith.busch@...el.com>

commit f55adad601c6a97c8c9628195453e0fb23b4a0ae upstream.

We don't need to zero fill the bio if not using kernel allocated pages.

Fixes: f3587d76da05 ("block: Clear kernel memory before copying to user") # v4.20-rc2
Reported-by: Todd Aiken <taiken@...ech.ca>
Cc: Laurence Oberman <loberman@...hat.com>
Cc: stable@...r.kernel.org
Cc: Bart Van Assche <bvanassche@....org>
Tested-by: Laurence Oberman <loberman@...hat.com>
Signed-off-by: Keith Busch <keith.busch@...el.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 block/bio.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/block/bio.c
+++ b/block/bio.c
@@ -1262,7 +1262,8 @@ struct bio *bio_copy_user_iov(struct req
 		if (ret)
 			goto cleanup;
 	} else {
-		zero_fill_bio(bio);
+		if (bmd->is_our_pages)
+			zero_fill_bio(bio);
 		iov_iter_advance(iter, bio->bi_iter.bi_size);
 	}